/*
 *  Copyright (C) 2005-2017 Apple Inc. All rights reserved.
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Library General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Library General Public License for more details.
 *
 *  You should have received a copy of the GNU Library General Public License
 *  along with this library; see the file COPYING.LIB.  If not, write to
 *  the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 *  Boston, MA 02110-1301, USA.
 *
 */

// RefPtr and PassRefPtr are documented at http://webkit.org/coding/RefPtr.html

#ifndef WTF_RefPtr_h
#define WTF_RefPtr_h

#include <algorithm>
#include <utility>
#include "FastMalloc.h"
#include "GetPtr.h"
#include "PassRefPtr.h"

namespace WTF {

    template<typename T>
    class RefPtr;

    template<typename T>
    RefPtr<T> adoptRef(T *);

    template<typename T>
    class RefPtr {
    WTF_MAKE_FAST_ALLOCATED;
    public:
        typedef T ValueType;
        typedef ValueType *PtrType;

        static constexpr bool isRefPtr = true;

        ALWAYS_INLINE RefPtr() : m_ptr(nullptr) {}

        ALWAYS_INLINE RefPtr(T *ptr) : m_ptr(ptr) { refIfNotNull(ptr); }

        ALWAYS_INLINE RefPtr(const RefPtr &o) : m_ptr(o.m_ptr) { refIfNotNull(m_ptr); }

        template<typename U>
        RefPtr(const RefPtr<U> &o) : m_ptr(o.get()) { refIfNotNull(m_ptr); }

        ALWAYS_INLINE RefPtr(RefPtr &&o) : m_ptr(o.leakRef()) {}

        template<typename U>
        RefPtr(RefPtr<U> &&o) : m_ptr(o.leakRef()) {}

        // See comments in PassRefPtr.h for an explanation of why this takes a const reference.
        template<typename U>
        RefPtr(const PassRefPtr<U> &);

        template<typename U>
        RefPtr(Ref<U> &&);

        // Hash table deleted values, which are only constructed and never copied or destroyed.
        RefPtr(HashTableDeletedValueType) : m_ptr(hashTableDeletedValue()) {}

        bool isHashTableDeletedValue() const { return m_ptr == hashTableDeletedValue(); }

        ALWAYS_INLINE ~RefPtr() { derefIfNotNull(std::exchange(m_ptr, nullptr)); }

        T *get() const { return m_ptr; }

        // FIXME: Remove release() and change all call sites to call WTFMove().
        RefPtr<T> release() {
            RefPtr<T> tmp = adoptRef(m_ptr);
            m_ptr = nullptr;
            return tmp;
        }

        Ref<T> releaseNonNull() {
            ASSERT(m_ptr);
            Ref<T> tmp(adoptRef(*m_ptr));
            m_ptr = nullptr;
            return tmp;
        }

        Ref<const T> releaseConstNonNull() {
            ASSERT(m_ptr);
            Ref<const T> tmp(adoptRef(*m_ptr));
            m_ptr = nullptr;
            return tmp;
        }

        T *leakRef() WARN_UNUSED_RETURN;

        T &operator*() const {
            ASSERT(m_ptr);
            return *m_ptr;
        }

        ALWAYS_INLINE T *operator->() const { return m_ptr; }

        bool operator!() const { return !m_ptr; }

        // This conversion operator allows implicit conversion to bool but not to other integer types.
        typedef T *(RefPtr::*UnspecifiedBoolType);

        operator UnspecifiedBoolType() const { return m_ptr ? &RefPtr::m_ptr : nullptr; }

        RefPtr &operator=(const RefPtr &);

        RefPtr &operator=(T *);

        RefPtr &operator=(std::nullptr_t);

        RefPtr &operator=(const PassRefPtr<T> &);

        template<typename U>
        RefPtr &operator=(const RefPtr<U> &);

        template<typename U>
        RefPtr &operator=(const PassRefPtr<U> &);

        RefPtr &operator=(RefPtr &&);

        template<typename U>
        RefPtr &operator=(RefPtr<U> &&);

        template<typename U>
        RefPtr &operator=(Ref<U> &&);

        void swap(RefPtr &);

        static T *hashTableDeletedValue() { return reinterpret_cast<T *>(-1); }

#if COMPILER_SUPPORTS(CXX_REFERENCE_QUALIFIED_FUNCTIONS)

        RefPtr copyRef() && = delete;

        RefPtr copyRef() const &WARN_UNUSED_RETURN { return RefPtr(m_ptr); }

#else
        RefPtr copyRef() const WARN_UNUSED_RETURN { return RefPtr(m_ptr); }
#endif

    private:
        friend RefPtr adoptRef<T>(T *);

        enum AdoptTag {
            Adopt
        };

        RefPtr(T *ptr, AdoptTag) : m_ptr(ptr) {}

        T *m_ptr;
    };

    template<typename T>
    template<typename U>
    inline RefPtr<T>::RefPtr(const PassRefPtr<U> &o)
            : m_ptr(o.leakRef()) {
    }

    template<typename T>
    template<typename U>
    inline RefPtr<T>::RefPtr(Ref<U> &&reference)
            : m_ptr(&reference.leakRef()) {
    }

    template<typename T>
    inline T *RefPtr<T>::leakRef() {
        return std::exchange(m_ptr, nullptr);
    }

    template<typename T>
    inline RefPtr<T> &RefPtr<T>::operator=(const RefPtr &o) {
        RefPtr ptr = o;
        swap(ptr);
        return *this;
    }

    template<typename T>
    template<typename U>
    inline RefPtr<T> &RefPtr<T>::operator=(const RefPtr<U> &o) {
        RefPtr ptr = o;
        swap(ptr);
        return *this;
    }

    template<typename T>
    inline RefPtr<T> &RefPtr<T>::operator=(T *optr) {
        RefPtr ptr = optr;
        swap(ptr);
        return *this;
    }

    template<typename T>
    inline RefPtr<T> &RefPtr<T>::operator=(std::nullptr_t) {
        derefIfNotNull(std::exchange(m_ptr, nullptr));
        return *this;
    }

    template<typename T>
    inline RefPtr<T> &RefPtr<T>::operator=(const PassRefPtr<T> &o) {
        RefPtr ptr = o;
        swap(ptr);
        return *this;
    }

    template<typename T>
    template<typename U>
    inline RefPtr<T> &RefPtr<T>::operator=(const PassRefPtr<U> &o) {
        RefPtr ptr = o;
        swap(ptr);
        return *this;
    }

    template<typename T>
    inline RefPtr<T> &RefPtr<T>::operator=(RefPtr &&o) {
        RefPtr ptr = WTFMove(o);
        swap(ptr);
        return *this;
    }

    template<typename T>
    template<typename U>
    inline RefPtr<T> &RefPtr<T>::operator=(RefPtr<U> &&o) {
        RefPtr ptr = WTFMove(o);
        swap(ptr);
        return *this;
    }

    template<typename T>
    template<typename U>
    inline RefPtr<T> &RefPtr<T>::operator=(Ref<U> &&reference) {
        RefPtr ptr = WTFMove(reference);
        swap(ptr);
        return *this;
    }

    template<class T>
    inline void RefPtr<T>::swap(RefPtr &o) {
        std::swap(m_ptr, o.m_ptr);
    }

    template<class T>
    inline void swap(RefPtr<T> &a, RefPtr<T> &b) {
        a.swap(b);
    }

    template<typename T, typename U>
    inline bool operator==(const RefPtr<T> &a, const RefPtr<U> &b) {
        return a.get() == b.get();
    }

    template<typename T, typename U>
    inline bool operator==(const RefPtr<T> &a, U *b) {
        return a.get() == b;
    }

    template<typename T, typename U>
    inline bool operator==(T *a, const RefPtr<U> &b) {
        return a == b.get();
    }

    template<typename T, typename U>
    inline bool operator!=(const RefPtr<T> &a, const RefPtr<U> &b) {
        return a.get() != b.get();
    }

    template<typename T, typename U>
    inline bool operator!=(const RefPtr<T> &a, U *b) {
        return a.get() != b;
    }

    template<typename T, typename U>
    inline bool operator!=(T *a, const RefPtr<U> &b) {
        return a != b.get();
    }

    template<typename T, typename U>
    inline RefPtr<T> static_pointer_cast(const RefPtr<U> &p) {
        return RefPtr<T>(static_cast<T *>(p.get()));
    }

    template<typename T>
    struct IsSmartPtr<RefPtr<T>> {
        static const bool value = true;
    };

    template<typename T>
    inline RefPtr<T> adoptRef(T *p) {
        adopted(p);
        return RefPtr<T>(p, RefPtr<T>::Adopt);
    }

    template<typename T>
    inline RefPtr<T> makeRefPtr(T *pointer) {
        return pointer;
    }

    template<typename T>
    inline RefPtr<T> makeRefPtr(T &reference) {
        return &reference;
    }

} // namespace WTF

using WTF::RefPtr;
using WTF::adoptRef;
using WTF::makeRefPtr;
using WTF::static_pointer_cast;

#endif // WTF_RefPtr_h
